1. Field of the Invention
The present invention relates to semiconductor devices, and more particularly, to methods of forming fuses for semiconductor devices and related structures.
2. Description of the Related Art
Memory capacities of semiconductor memory devices are continuously increased by reducing sizes of individual elements therein. As the density of the elements per unit area increases by reducing sizes of elements, defect rates of elements may increase. An integrated circuit chip including a single defective element may be considered a failure resulting in reduced yield.
To increase yields, a redundant (or spare) circuit can be provided in a chip to replace a defective element. The replacement of a redundant circuit for an inoperative circuit can be referred to as a repair operation. In addition, a trimming operation of varying characteristics of some circuits for application may be performed.
Repair and/or trimming operations can be performed by cutting portions of wires with a laser. The wires cut with the laser can be referred to as fuses. A region having a plurality of fuses can be referred to as a fuse region. Because cut fuses can block current flow, a high conductive state can be converted into a low conductive state, for example, a non-conductive state.
FIG. 1 illustrates a fuse region 10 having a plurality of fuses 2, 4, 6, and 8. The plurality of fuses 2, 4, 6, and 8 shown in FIG. 1 are in an uncut state, namely, in the conductive state.
Referring to FIG. 2, the fuse 4 is cut by irradiating a laser thereon so as to block the current flowing through the fuse 4. The cut fuse 4 and adjacent fuses 2 and 6 may be relatively near each other in considering the laser wavelength and the spot size. Accordingly, adjacent fuses may be accidentally cut in a fuse cutting operation. As a result, a defect may be introduced into the semiconductor device, a link to adjacent regions may be generated, and/or severe physical damage may occur in adjacent fuses. In addition, a crack 11 caused by stress from laser energy may develop from the fuse 4 so that adjacent fuses are damaged.
Methods for protecting adjacent fuses in a fuse cutting operation have been developed. A sufficient distance can be maintained between fuses so that excessive cracks and/or damage on the adjacent elements and/or on adjacent fuses is reduced. However, as semiconductor devices become more highly integrated, dense pitches may be required between the wires. Accordingly, a crack blocking structure may be interposed between fuses to reduce distance of the pitch or a fuse pattern may be varied to form a highly reliable fuse region.
FIG. 3 illustrates a fuse region 20 formed of a plurality of fuses 12, 14, and 16. Additional structures 23 and 25 are arranged between the fuses in the fuse region 20. The additional structures 23 and 25 are formed of a barrier material, such as tungsten or molybdenum, operating as a crack stop portion in cutting the fuse 14 with the laser. As a result, a crack 21 developed from the fuse 14 may be blocked by the additional structures 23 and 25.
However, even though this method may reduce a gap between the pitches to a certain degree, a gap between pitches may be increased by adding the additional structures and an increase of chip area may result. Moreover, the crack stop structures introduced between the fuses may be inoperative in a dense pitch, because the crack stop structures themselves may be ablated by the laser, thereby damaging adjacent fuses or circuit elements.
In the case of a DRAM, bit lines or word lines may be used as fuses. In semiconductor devices other than the memory devices, other wires may be used as fuses. Recently, metal wires have been used as fuses in DRAMs. When metal wires are used as fuses, thicknesses and widths of the metal wires may be relatively greater than those of the bit lines or the word lines.